This invention relates generally to assembling rotatable machinery and, more particularly, to methods and systems for sealing an extraction cavity in a steam turbine.
At least some known steam turbine designs include static nozzle segments that direct a flow of steam into blades coupled to a rotatable member in the turbine. A nozzle airfoil construction is typically called a diaphragm stage. When more than one nozzle stage is supported by an outer structure or ring, the construction is generally referred to as a nozzle carrier, a “drum construction”, or a “carrier construction” flowpath. A nozzle carrier is supported within a turbine casing such that the nozzles are substantially aligned with stages of the turbine blades.
In at least some known turbines, steam is extracted from the low-pressure turbine section for use in other applications. Generally, in steam turbines including a nozzle carrier, steam may only be extracted from the turbine section downstream from a last stage of the carrier. However, in some cases, this extraction location may not be the optimum stage from which steam should be extracted. For example, often a higher pressure or higher temperature steam is desired.
Accordingly, at least some known steam turbines utilize separate carriers within the turbine design to enable steam to be extracted from a location defined between the first and the second carriers. However, utilizing separate carriers may make alignment difficult, as both the carrier and the rotor must be removed to make necessary adjustments. Moreover, utilizing separate carriers generally adds complexity to a turbine design that the carrier is intended to improve. As such, costs and/or time associated with fabrication, assembly, and/or maintenance of the turbine may be increased.